The present invention relates in general to shaft seals, and in particular to a new and useful sealing arrangement which utilizes a first seal ring connected to and rotating with a shaft, which is surrounded on its radially extending and circumferentially extending surfaces, by a non-rotating seal ring connected to a housing.
A shaft seal according to co-pending U.S. patent application Ser. No. 500,160 filed June 1, 1983 entitled SHAFT SEAL WITH POSITIVELY MAGNETICALLY CONTROLLED SEAL GAP (German patent application No. P 32 21 380.8-12) operates to maintain a narrow sealing gap at all speeds and independently of the pressure of the sealing fluid, so that the fluid leakage is small. This co-pending application is incorporated here by reference.
In such a design, the sealing gap is formed preferably between one of the front sides of a rotating seal ring and an associated non-rotating seal ring, and is kept constant by means of electronically controlled electromagnets. With the use of two different sealing fluids or with a sealing fluid pressure graduation, a sealing gap may be provided at either front side of the rotating seal ring. Such a double seal then comprises two complete sealing systems which require a considerable space and an electronic control which is very expensive.